Question: Tiffany did 56 fewer sit-ups than Nadia in the evening. Nadia did 99 sit-ups. How many sit-ups did Tiffany do?
Explanation: Nadia did 99 sit-ups, and Tiffany did 56 fewer than that, so find the difference. The difference is $99 - 56$ sit-ups. She did $99 - 56 = 43$ sit-ups.